This invention relates to gear pumps and more particularly to gear pumps adapted to pump contaminated fluid.
Many fuel supply systems for gas turbine engines employ high pressure gear pumps to furnished engine fuel. In addition, such pumps may provide hydraulic supply pressure for actuator systems.
A typical gear pump embodies a pair of steel gears connected to shaft journals which turn in bronze bearings. The bearings include passages which extend from the bearing faces to the bearing interiors for lubricating and cooling the bearing surfaces of the shaft journals. Obviously, the passages must be of a sufficient size to insure that no clogging will be occasioned by contaminants in the fluid being pumped. The main problem encountered in using large lubrication passages is the diminution of the pumps volumetric efficiency.
An alternative approach is to provide a source of filtered fluid for lubrication purposes. This arrangement necessarily entails the use of either a barrier or wash flow type filter and appropriate housing coring to direct filtered fluid to the bearings.